Table 2.

Examples of some terpenes that are primarily produced by plants and their antiviral activity and mechanism of action

Volatile terpen compound	Used technique	Test influenza strain	Mechanism of action	References
	In vitro	H1N1- 4 strains, H3N2-2 strains, H9N2-2 strains, H5N1-1 strain	1. Disrupts the viral reproduction and the subsequent hypercytokinemia 2. Inhibition or reduction in the interaction of NA and HA proteins 3. Prolongs cell proliferation	[56, 57]
	In vitro, in vivo	H1N1-2 strains, H3N2-2 strains, Influenza B virus-1	Interferes with the transcription machinery and attachment of the virus proteins prior and during the infectious process	[58, 59]
	In vitro, in vivo	H1N1-2 strains, H2N2-1 strain, H3N2-1strain, Influenza B virus-1 strain	1. Disrupts the viral reproduction and the subsequent hypercytokinemia 2. Inhibition or reduction in the interaction of NA and HA proteins	[59–62]
	In vitro	H3N2-1 strain, H1N1-1 strain	Interacts with the translation process of the viral genome to reduce the amount of the produced mRNA	[59, 63]
	In vitro	H1N1-1 strain	Causes reduction in cell transportation networking during the acidification process	[64–66]
	In vitro	H1N1-1 strain	Causes reduction in cell transportation networking during the acidification process	[65, 66]
	In vitro	H1N1- 1 strain	Causes reduction in cell transportation networking during the acidification process	[65, 66]